View Full Version : Proper use of lathe cutting tools?? Online diagrams or help?
04-21-2003, 11:32 AM
I'm new to the lathe and I am experancing a few setbacks....
For my cutting tools, I have bought a set of carbide inserts with holders:
I think I have the TT or TCMM style???
While trying to face a 1" shaft last night, I broke one insert and pretty much gave up.
About the only things I know that is correct is that my tool should be at the centerline of the part and the direction of the part rotation...other than that, I'm not sure if my approach angle is correct or how should the insert "approach" the part for facing or cutting material???
Should the body of the tool holder be parallel with the lathe chuck or a few degrees off.
04-21-2003, 12:37 PM
Sorry, I cannot help as I always use HSS tool bits. I've never had any good experiences with Cemented carbides simply because I don't know how to use them properly.
04-21-2003, 01:11 PM
Mueller once again the best advice any of us can give you is find out if there is a local community college or tech school that has evening classes in machine shop. And if there are shop classes available find out who the guys or gals are who take the classes repeatedly. Ask questions. And no you will not be asking "dumb questions". I have yet to meet any one who refuses to share their knowledge as long as you are willing to listen. With the exception of some square headed Germans when I started my apprenticeship http://bbs.homeshopmachinist.net//rolleyes.gif
04-21-2003, 03:12 PM
Several things that can be causing the carbide to chip.
- Rigid setup is essential for carbide cutters. Carbide is brittle so any chatter or interruption in the cut will cause it to chip. Minimize the over hang of the holder.
- Either use no cooling fluid or flood it, since anything in between can cause the carbide to crack.
- The inserts that come with these low cost Chinese imports are needless to say poor quality. Frankly, I've only had bad experience with them. Find a good quality domestic and try again.
- Replace the screws that hold down the carbide. The ones that came with the holder will strip before you can apply the necessary torque. A good quality high strength screws are expensive (relative to the set that you bought) but in the long run you'll actually save money, time, and frustration.
Most importantly, don't give up. Once you have it figured out, you can increase the speed of your lathe by 2 to 3 times, and make some beautiful looking cuts.
04-21-2003, 04:06 PM
http://users.aol.com/lughaid/cuttools.jpg shapes vs direction of travel.Courtesy of "A lot of brass" website..
I am still learning too, more every day.
I have not had any luck with the foriegn cutters. ie:brazed on tips.
[This message has been edited by ibewgypsie (edited 04-21-2003).]
[This message has been edited by ibewgypsie (edited 04-21-2003).]
04-21-2003, 08:20 PM
I have also not had much luck with brazed on carbide cutters. I found that some didn't have cutting edges yet, and were basically just chunks of carbide waiting for further processing. I would take them back and ask for someone to check to see if they're ok, or if they're defective. Other than that, my recommendation is to stay away from carbide until you have played with hss for awhile.
He doesn't have brazed, they are removable insert tools. I have some and they are "OK".
They break if you:
*don't tighten down right
*tighten onto swarf or a burr on the seat
*do interrupted cuts at a high feed
*try to back out after stalling in a cut
*have a dig in
*feed roughly or too fast
*get excessive build up on the point of the tool, as with hot rolled steel, or some aluminum (use oil brushed on, or WD40 for Aluminum)
Don't toss chipped inserts. They are perfect for roughing cuts on cast iron, where you would be afraid of damaging the cutter on sand or scale. If you chip it again, who cares?
This depends on how the tip looks, of course. A diamond hone can fix up enough to get going though.
04-22-2003, 09:31 PM
While Daryrl was speaking of brazed carbide and you have inserts what he said may be very valid in your case. I bought much the same set you have from Harbor Freight (yours looks like the same one Little Machine Shop has (www.littlemachineshop.com). His inserts are cheaper btw.
Oso (the bear?) seems to have it about all the ways you (ha! and I) can chip a carbide tool. "try to back out after stalling in a cut" OK so how do you get the tool out if ya don't back it out - huh?
Now I went and bought a carbide tool grinder and when I cleaned up some of my chipped up carbide tools I found two things -
1 - they did not even have 5* relief on them and
2 - they are 10 times sharper now than they were -
Now they not only LOOK like they have an edge on them, they cut like its butter! I likely don't run them as hard as you are supposed to for carbide but I sure do like the way they work. Now that I have the tool grinder I can put a decent point on HTS - sure did butcher them by hand.
04-22-2003, 10:31 PM
Meuller: If you are new to lathes work, I would suggest HSS. HSS is a litle more forgivng. I have helped couple of men learn their lathes. First set ups were always ragged- even with HSS. After they learned to set up correctly, they could not duplicate the troubles they were having. They had learned what to do and forgot the troubles they had at first. So go for HSS until you can make it work by instinct then go for carbide.
[This message has been edited by docsteve66 (edited 04-22-2003).]
04-23-2003, 08:52 AM
May not be the problem, but keep setups short. ie Work close to the chuck, and choke up on the cutting tool.
A carriage stop on the bed can be used to keep from crashing into the chuck.
The angle of the cutting edge to the work is a finer point and is changed for different situations/preferences. If the depth of cut is less than the radius on the end of the insert, it matters even less.
Like an old freind said over and over when talking about an amorous situation (that never jelled), "I'm gonna - take it easy the first time." Start with shallow cuts and work up from there.
Here's a link to some free old textbook downloads.
04-23-2003, 02:18 PM
I bought a cheapo asian set of 5 holders and inserts. The problem was the holders were made for positive rake inserts but they sent me negative inserts. They couldn't cut for beans! Bought some CCMT*** inserts from www.carbidedepot.com/ (http://www.carbidedepot.com/) for $2.00@ now they cut like butter!
04-23-2003, 04:22 PM
You have not mentioned the set up.. are you above center? below center with your tool? I found out cutting real close to center with the taiwan tool post I did have was disaster waiting to happen. The toolpost had way too much flex in it. I since have gotten a better one, alas, still not a aloris..